Investments - Consolidated Statements of Assets and Liabilities for PSSL (Parenthetical) (Details) - USD ($) $ in Thousands |
Mar. 31, 2026 |
Sep. 30, 2025 |
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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Investments at cost | $ 2,646,425 | [1],[2],[3],[4] | $ 2,819,393 | [5],[6],[7],[8] | ||||||||||||||||
| Cash and cash equivalents, cost | 31,427 | 40,729 | ||||||||||||||||||
| Cash equivalents at cost | 31,427 | 40,729 | ||||||||||||||||||
| Cash At Cost | 90,446 | [3],[4] | 81,955 | [7],[8] | ||||||||||||||||
| Unfunded commitments to fund investments | 600 | 400 | ||||||||||||||||||
| PennantPark Senior Secured Loan Fund I LLC | ||||||||||||||||||||
| Investments at cost | 1,238,389 | 1,103,716 | ||||||||||||||||||
| Cash equivalents at cost | 18,001 | 47,870 | ||||||||||||||||||
| Cash At Cost | 15,997 | 13,690 | ||||||||||||||||||
| 2036 Asset-backed debt, net | 246,000 | 246,000 | ||||||||||||||||||
| 2037 Asset-backed debt, net | 246,000 | 246,000 | ||||||||||||||||||
| 2037 R Asset-backed debt, net | 246,000 | 246,000 | ||||||||||||||||||
| PennantPark Senior Secured Loan Fund II LLC | ||||||||||||||||||||
| Investments at cost | 340,545 | |||||||||||||||||||
| Cash equivalents at cost | 5,320 | |||||||||||||||||||
| Cash At Cost | 9,169 | |||||||||||||||||||
| 2036 Asset-backed debt | PennantPark Senior Secured Loan Fund I LLC | ||||||||||||||||||||
| Unamortized Deferred Financing Costs | 1,197 | 1,341 | ||||||||||||||||||
| 2037 Asset-Backed Debt | PennantPark Senior Secured Loan Fund I LLC | ||||||||||||||||||||
| Unamortized Deferred Financing Costs | 1,732 | 1,904 | ||||||||||||||||||
| 2037 R Asset-backed debt | PennantPark Senior Secured Loan Fund I LLC | ||||||||||||||||||||
| Unamortized Deferred Financing Costs | $ 2,296 | $ 2,518 | ||||||||||||||||||
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